Easily unsealable packaging body and method of manufacturing the same

ABSTRACT

An easy-open packaging body  1  includes: a container body  10  with a flange  14  formed on a circumference of an opening  13 , and a cover  20  heat-sealed to the flange  14  to close the opening  13 . Inner and outer notches  15 A and  15 B enclosing the opening  13  are formed respectively on inner and outer circumferential sides on the flange  14 . The flange  14  and the cover  20  are heat-sealed by a first seal part  16 A having a predetermined width and formed between the inner and outer notches  15 A and  15 B to enclose the opening  13  and a second seal part  16 B having a width narrower than that of the first seal part  16 A and formed within an area of the first seal part  16 A to enclose the opening  13  along the first seal part  16 A, the second seal part  16 B having a projected seal part  17  projected outward relative to the other part on a position corresponding to a tab  21.

TECHNICAL FIELD

The present invention relates to an easy-open packaging body and amanufacturing method of the same.

BACKGROUND ART

For a packaging body formed by filling a container with contents such asfood and heat-sealing a cover to the container, high sealing performanceis desired in terms of keeping quality of the contents, which requiressealing with high heat-sealing strength. On the other hand, in terms ofusability in using the contents, the packaging body should preferably beopened with small force, in other words, easy-open performance isdesired. Various methods have been suggested for satisfying the sealingperformance and easy-open performance as contradictory performances.

Especially, there have been suggested a method for adjusting adhesivestrength of a heat-sealed interface by controlling heat-sealingcondition in sealing a container by heat-sealing a flange extending froman opening of the container in an outer circumferential direction and acover, and a method for forming a container such that at least aninnermost layer of the container is peeled off with a cover when thecover is opened.

In terms of securing rigidity of the container to meet size increase,shape change, and thickness reduction of the container for resourcesaving, it has been suggested increasing the width of a flange of thecontainer, providing a flange with a skirt having a bent part that isformed by bending an outer circumferential end of the flange; providinga flange with a curl formed by bending an outer circumferential end ofthe flange to have a substantially C-shaped cross section.

In the container with the uniquely-shaped flange having the skirt or thecurl, when the flange of the container and the cover are heat-sealed, itis required to peel off the innermost layer of the container with thecover while leaving a part other than a heat-sealed part of the flange.Thus, it might become even more difficult to realize the easy-openperformance while keeping the sealing performance.

In order to solve the problem, a new easy-open container has beensuggested (see, for instance, Japanese Patent Publication No. 2724355,left column of page 3 and FIG. 1).

In the disclosed technique, ringed inner and outer notches arerespectively provided on the inner and outer circumferential sides of aflange to enclose an opening of the container, and a melt-seal part isformed between the inner and the outer notches so that the flange andthe cover adhere to each other. A projected seal part projected outwardrelative to the outer notch is formed on the melt-seal part on aposition corresponding to a tab of the cover. A dent is formed on aninner layer of the container positioned on an outer edge of theprojected seal part. In the easy-open container, when the cover ispeeled off from the container, the dent formed on the outer edge of theprojected seal part serves as a trigger of the peeling, andsubsequently, the cover is gradually peeled off along the outer notch.

However in the technique described above, when the contents of thecontainer are food, the contents are contained and then boiled or heatedfor sterilization after forming the container and the notches. Sincepositions of the notches are slightly displaced due to the heating, aheat-seal position cannot be placed between the two notches and theheat-sealing is provided on an area out of the notches, which causesproblem in sealing performance of the container. If, for instance,adhesive strength between the cover and the container is increased tosolve the problem of the sealing performance, then peeling with smallforce becomes difficult, so that the easy-open performance cannot berealized. As a result, both of the sealing performance and the easy-openperformance cannot be achieved at the same time.

In addition, in forming the dent on the outer edge of the projected sealpart, a dent is formed on a position other than the predeterminedposition described above, which causes the peeling to start from theouter circumferential end of the heat-sealed part instead of from theouter notch, so that it is difficult to manufacture the container withconsistent quality.

DISCLOSURE OF THE INVENTION

An object of the present invention is to provide an easy-open packagingbody satisfying both of sealing performance and easy-open performancewith consistent quality and a manufacturing method of the same.

An easy-open packaging body according to an aspect of the presentinvention formed by molding a multilayer sheet, includes: a containerbody including an opening and a flange formed on a circumference of theopening; and a cover that is heat-sealed to the flange to close theopening, the cover having an open trigger formed on an outercircumference thereof: when the cover is peeled off from the opentrigger, at least an innermost layer of the container body which isheat-sealed on the flange is peeled off with the cover in opening; aninner notch and an outer notch each enclosing the opening are formedrespectively on an inner circumferential side and an outercircumferential side of the flange; the flange and the cover areheat-sealed by a first seal part having a predetermined width and formedbetween the inner notch and the outer notch and a second seal parthaving a width narrower than that of the first seal part and formedwithin an area of the first seal part to enclose the opening along thefirst seal part; and the second seal part has a projected part projectedoutward relative to the other part thereof at a position correspondingto the open trigger.

Herein, in order to peel off at least the innermost layer of the flangeof the container together with the cover, the peeling strength should be4 to 15 N/15 mm, more preferably, 8 to 12 N/15 mm. The sealing strengthbetween the flange of the container and the cover should be equal to orhigher than 23 N/15 mm.

The shape of the projected part is not limited specifically, andtriangular, trapezoidal, quadrangular and semicircular shapes can beexemplified.

The shape and size of a tip end and a base end of the projected part arenot limited specifically either, but the base end is preferably roundedin the outer circumferential direction.

Further, the number of the projected part is not limited either as longas there is one or more projected parts. When a plurality of projectedseal parts are provided, the projected seal parts are preferablyarranged at even intervals for applying balanced stress in peeling.

According to the present invention, the first seal part keeps thesealing performance of the packaging body, while the projected part ofthe second seal part serves as a trigger of the peeling in peeling offthe cover and provides smooth peeling. Since the strong heat-sealing isprovided, the sealing performance can be enhanced. That is to say, whenthe cover is peeled off from the container body, at least the inner mostlayer of the flange is lifted, and the entire circumference of theinnermost layer of the heat-sealed part is peeled off. Thus, since theproblem in sealing performance caused by an arrangement where theheating is performed for sterilization of the contents after forming thecontainer body and the notches and the heat-sealing is provided out ofthe area between the notches does not occur, and thus the problem doesnot have to be solved with excessive adhesive strength of the first sealpart. Therefore, the easy-open performance is not degraded, and thesealing performance and the easy-open performance can be achieved at thesame time.

By providing the second seal part, the second seal part serves as thetrigger of the peeling in peeling off the cover. Thus, unlike theconventional arrangement, the problem where, in forming the dent forpeeling, a dent is formed on a position other than the predeterminedposition, causing the peeling to start from the outer circumferentialend of the heat-sealed part instead of from the outer notch does notoccur, so that the easy-open packaging body with consistent quality canbe provided.

In the easy-open packaging body of the present invention, the tip end ofthe projected part may be positioned on an inner side of the outer notchas long as the distance is equal to or less than 0.5 mm.

With the arrangement, by positioning the tip end of the projected parton the inner side relative to the outer notch, resin used for formingthe projected seal part will not flow into the outer notch, so that thepeeling of the cover will not be affected.

In the easy-open packaging body according to the present invention, itis preferable that an inner circumferential side of the first seal partand the inner notch are spaced apart. The spaced distance isapproximately 0.2 to 5 mm.

With the arrangement, since the inner circumferential side of the firstseal part and the inner notch are spaced apart, if the pressure insidethe packaging body increases, the stress concentrates on the innercircumferential side of the first seal part, so that the peeling frominner side does not occur even with the arrangement in which at leastthe innermost layer of the flange of the container is easily peeled offfrom the notch.

In the easy-open packaging body according to the present invention, itis preferable that the flange has a bent part formed by bending an outercircumferential end of the flange.

The bent part includes a so-called skirt type with the outercircumferential end of the flange merely being bent, a so-called curltype with the outer circumferential end being extended verticallydownward and bent to have substantially C-shaped or semicircular crosssection, and the like.

With the arrangement, since the flange has the bent part formed bybending the outer circumferential end thereof, rigidity of the containeris enhanced, thus flexibly meeting the size increase, shape change andthickness reduction of the container.

In the easy-open packaging body according to the present invention, itis preferable that the innermost layer is made of polypropylene resin,and the thickness of the innermost layer is 40 to 100 μm.

If the thickness is smaller than 40 μm, the pressure resistance might bedegraded. If the thickness exceeds 100 μm, it becomes difficult to formthe projected seal part.

In the easy-open packaging body according to the present invention, itis preferable that, when the innermost layer of the container body ispeeled off with the cover in opening, the innermost layer is peeled offby layer peeling generated between the innermost layer and an adjacentlayer adjacent to the innermost layer or cohesive peeling generatedwithin the adjacent layer.

With the arrangement, through the layer peeling generated between theinnermost layer and the adjacent layer adjacent to the innermost layeror the cohesive peeling generated within the adjacent layer, the coveris not peeled off from the innermost layer, which allows the sealingstrength between the cover and the innermost layer to be increased, sothat the packaging body can be easily opened without affecting thesealing performance.

According to another aspect of the present invention, a manufacturingmethod of an easy-open packaging body formed by molding a multilayersheet and including a container body including an opening and a flangeformed on a circumference of the opening and a cover that is heat-sealedto the flange to close the opening, the cover having an open trigger onan outer circumference of the cover, in which, when the cover is peeledoff from the open trigger, at least an innermost layer of the containerbody which is heat-sealed on the flange is peeled off with the cover inopening includes: a notch forming step for forming an inner notch and anouter notch each enclosing the opening respectively on an innercircumferential side and outer circumferential side of the flange; acontents filling step for filling the container body with contents; afirst heat-sealing step for forming a first seal part having apredetermined width between the inner notch and the outer notch toenclose the opening, and a second heat-sealing step for forming a secondseal part having a width narrower than that of the first seal part andformed within an area of the first seal part to enclose the openingalong the first seal part, the second seal part being projected outwardrelative to the other part on a position corresponding to the opentrigger.

According to the present invention, the first seal part keeps sealingperformance of the packaging body, while the projected part of thesecond seal part serves as a trigger of the peeling in peeling off thecover and provides smooth peeling. Since the strong heat-sealing isprovided, the sealing performance can be enhanced. That is to say, whenthe cover is peeled off from the container body, at least the inner mostlayer of the flange is lifted, and the entire circumference of theinnermost layer of the heat-sealed part is peeled off.

Therefore, since the problem in sealing performance caused by anarrangement where the heating is performed for sterilization of thecontents after forming the container body and the notches and theheat-sealing is provided out of the area between the notches does notoccur, and thus the problem does not have to be solved with excessiveadhesive strength of the first seal part. Therefore, the easy-openperformance is not degraded, and the sealing performance and theeasy-open performance can be achieved at the same time.

Thus, by providing the second seal part that serves as the trigger ofthe peeling in peeling off the cover, unlike the conventionalarrangement, a problem where, in forming the dent for peeling, a dent isformed on a position other than the predetermined position, causing thepeeling to start from the outer circumferential end of the heat-sealedpart instead of from the outer notch does not occur, so that theeasy-open packaging body with consistent quality can be provided.

In the manufacturing method of the easy-open packaging body according tothe present invention, it is preferable that the second heat-sealingstep is conducted under a condition with temperature and pressure higherthan those of the first heat-sealing step.

With the arrangement, by conducting the second heat-sealing step underthe condition having temperature and pressure as than those of the firstheat-sealing step, a dent is not generated on a position other than thepredetermined position when the heat-sealing is performed, and thus thepeeling does not start from the outer edge of the heat-sealed part, sothat the packaging body with high reliability can be provided.

In the manufacturing method of the easy-open packaging body according tothe present invention, it is preferable that heat-sealing temperature inthe second heat-sealing step is higher than that of the firstheat-sealing step by 5° C. or more.

If the heat-sealing temperature in the second heat-sealing step is nothigher than that of the first heat-sealing step by 5° C. or more, thepeeling cannot be started and further smoothness in peeling is degraded.Furthermore, the heat-sealing strength is lowered, which might cause aproblem in sealing performance.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a cross section showing an easy-open packaging body accordingto a first embodiment of the present invention;

FIG. 2 is a plan view showing the easy-open packaging body of theembodiment shown in FIG. 1; and

FIG. 3 is a cross section showing a flange of the embodiment shown inFIG. 1 in an enlarged manner.

BEST MODE FOR CARRYING OUT THE INVENTION

An embodiment of the present invention will be described below withreference to the attached drawings.

FIGS. 1 (side view), 2 (top view) and 3 (fragmentary sectional view ofFIG. 1) show an easy-open packaging body 1 according to the embodimentof the present invention.

The easy-open packaging body 1 includes a resin-made container body 10formed by molding a multilayer sheet and a circular cover 20 with anopening tab.

Although not shown, the cover 20 is formed by laminating three layers ofcast polypropylene, ethylene vinyl alcohol resin and nylon, in orderstarting from the side of the container body 10, the cover 20 includinga semicircular tab 21 as an open trigger. The outer diameter of thecover 20 is greater than that of a flange 14. The tab 21 is big enoughto be pinched for opening.

The container body 10 includes a circular bottom side 11, a cylindricallateral side 12 being upright from and integrated with the bottom side11, a circular opening 13 on a top side and the ringed flange 14extending outward from the circumference of the opening 13, which areintegrated to form the container body 10.

As shown in detail in FIG. 3, layers of the container body 10 include afirst layer 10A (the innermost layer), a second layer 10B, a third layer10C, a fourth layer 10D, a fifth layer 10E, a sixth layer 10F and aseventh layer 10G, in order starting from the inner side. Each of thelayers may be made of various resins such as polyolefin resin,polyethylene resin, polypropylene resin, ethylene vinyl alcohol resinand adhesive resin.

The first layer 10A is made of polyethylene resin or polypropylene resinwith thickness of 40 to 100 μm.

If the thickness is smaller than 40 μm, the pressure resistance might belowered. If the thickness exceeds 100 μm, it becomes difficult to form aprojected seal part 17 (described later).

The flange 14 has a bent part 14A formed by bending the outercircumferential end of the flange 14. The bent part 14A has a so-calledskirt shape with the outer circumferential end merely being bentdownward by 45°.

On the top side of the flange 14, inner and outer notches 15A and 15Beach enclosing the opening 13 are formed respectively on the inner andouter circumferential sides of the flange 14, and a heat-seal part 16 isconcentrically formed on an area between the inner and outer notches 15Aand 15B.

The inner and outer notches 15A and 15B have V-shaped cross sectionbeing gradually narrowed in depth direction, the depth of which issubstantially equal to the thickness of the first layer 10A of thecontainer body 10.

The cross section of the inner and outer notches 15A and 15B may also beU-shape, linear, semicircle arc and the like. The depth of the inner andouter notches 15A and 15B may be any depth as long as the first layer10A of the container body 10 can be easily cut when the cover 20 ispeeled off, which is preferably be greater as compared to the thicknessof the first layer 10A.

The heat-seal part 16 is welded on a back side of the cover 20, whichincludes a ringed first seal part 16A enclosing the opening 13 andhaving a predetermined width and a ringed second seal part 16B formedwithin an area of the first seal part 16A to enclose the opening 13along the first seal part 16A, the second seal part 16B being narrowerthan the first seal part 16A.

The inner circumferential side of the first seal part 16A and the innernotch 15A are spaced apart (shown by t in FIG. 3).

The second seal part 16B is formed along the central part of the firstseal part 16A in the width direction, the width of which is narrowerthan that of the first seal part 16A.

The second seal part 16B includes the projected seal part 17 that isprojected outward relative to the other part on a position correspondingto the tab 21 as the open trigger.

As shown in FIG. 2, the projected seal part 17 has a substantiallytriangular shape in plan view, the resin of the projected seal part 17being continuously connected to the resin of the second seal part 16B.

The easy-open packaging body 1 formed as described above is manufacturedas follows.

A resin-made multilayer sheet including multilayer (seven layers in thepresent embodiment), which is molded in advance by T-die extrusion,lamination or the like is pre-stretched using a plug in a cavity havinga shape corresponding to the profile of the container, and then thecontainer body 10 is manufactured by a plug assist molding where acontainer is molded by air-pressure molding or vacuum molding (containermolding step).

Then, by pressing a stamping die having ringed blades onto the top sideof the flange 14, the inner and outer notches 15A and 15B each enclosingthe opening 13 are formed respectively on the inner and outercircumferential sides of the flange 14 (notch forming step).

After the notch forming step, the container body 10 is filled withcontents (contents filling step), and the film cover 20 is welded ontothe flange 14 using a heat-seal device. The welded part in the abovestep becomes the heat-seal part 16.

Although not shown, the heat-seal device used herein is a widely-usedone, which includes a seal bucket for receiving the container body 10, acover feeder for feeding the film cover 20, and a seal ring movingvertically for sealing the cover 20 and the flange 14 of the containerbody 10.

First, the seal ring corresponding to the shape of the first seal part16A is pressed onto the top side of the flange 14 via the cover 20.

The first seal part 16A is formed in such a manner that the innercircumferential side of the first seal part 16A and the inner notch 15Aare spaced apart with a distance (t in FIG. 3) between the innercircumferential side of the first seal part 16A and the inner notch 15Abeing 0.2 to 5.0 mm (first heat-sealing step). The distance describedabove is required since the stress concentrates on the inner side of theringed seal part.

Next, a seal ring corresponding to the shape of the second seal part 16Bhaving the projected seal part 17 projected toward the outercircumferential side is pressed onto the top side of the flange 14 viathe cover 20, and the second seal part 16B having narrower width thanthe first seal part 16A and having the projected seal part 17 are formedwithin the area of the first seal part 16A to enclose the opening 13along the first seal part 16A (second heat-sealing step).

The second heat-sealing step is conducted under the condition havingtemperature and pressure higher than that of the first heat-sealingstep.

The heat-sealing temperature in the second heat-sealing step is higherthan that of the first heat-sealing step by 5° C. or more.

If the heat-sealing temperature in the second heat-sealing step is nothigher than that of the first heat-sealing step by 5° C. or more, thepeeling cannot be started and further smoothness in peeling is degraded.In addition, the heat-sealing strength is lowered, which might cause aproblem in sealing performance.

Referring to FIG. 3, first, the tab 21 is gripped to peel off the cover20 to open the easy-open packaging body 1.

The second seal part 16B having the projected seal part 17 serves as atrigger of the peeling when the cover 20 is peeled off. When the cover20 is peeled off from the container body 10, the first layer 10A of theflange 14 is lifted, and the entire circumference of the first layer 10Aof the heat-sealed part is peeled off. After the peeling is started, thefirst layer 10A is cut at the outer notch 15B, which causes layerpeeling between the first layer 10A and the second layer 10B.

When the layer peeling between the first layer 10A and the second layer10B reaches the inner notch 15A, the first layer 10A is cut at the outernotch 15B (Translator's comment: correctly, inner notch 15A). At thistime, the first layer 10A on a part between the inner and outer notches15A and 15B is adhered to the cover 20.

The present embodiment described above provides advantages as follows.

(1) The first seal part 16A keeps sealing performance of the easy-openpackaging body 1, while the second seal part 16B having the projectedseal part 17 (projected part) serves as a trigger of the peeling inpeeling off the cover 20 and provides smooth peeling. Since the strongheat-sealing is provided, the sealing performance can be enhanced. Whenthe cover 20 is peeled off from the container body 10, at least thefirst layer 10A of the flange 14 is lifted, and the entire circumferenceof the first layer 10A of the heat-seal part 16 is peeled off.Therefore, since the problem in sealing performance caused by anarrangement where the heating is performed for sterilization of thecontents after forming the container body 10 and the inner and outernotches 15A and 15B and the heat-sealing is provided out of the areabetween the inner and outer notches 15A and 15B does not occur, and thusthe problem does not have to be solved with excessive adhesive strengthof the first seal part 16A. Accordingly, the easy-open performance isnot degraded, and the sealing performance and the easy-open performancecan be achieved at the same time

By providing the second seal part 16B, the second seal part 16B servesas the trigger in peeling off the cover 20. Thus unlike the conventionalarrangement, a problem where, in forming the dent for peeling, a dentnot formed on a position other than the predetermined position, causingthe peeling to start from the outer circumferential end of theheat-sealed part instead of from the outer notch does not occur, so thatthe easy-open packaging body 1 with consistent quality can be provided.

(2) When the tip end of the projected seal part 17 is positioned on theinner side relative to the outer notch 15B, resin for forming theprojected seal part 17 does not flow into the outer notch 15B, so thatthe peeling of the cover 20 is not impeded.

(3) Since the inner circumferential side of the first seal part 16A andthe inner notch 15A are spaced apart by the distance t, even when thepressure inside the packaging body increases, the stress concentrates onthe inner circumferential side of the first seal part 16A, so that thepeeling from the inner side does not occur even with the arrangementwhere at least the innermost layer of the flange 14 of the container iseasily peeled off from the notch.(4) Since the flange 14 has the bent part 14A formed by bending theouter circumferential end thereof, rigidity of the container body 10 isenhanced, thus flexibly meeting the size increase, shape change andthickness reduction of the container.(5) Due to the layer peeling between the first layer 10A and theadjacent second layer 10B adjacent to the first layer 10A, the cover 20is not peeled off from the first layer 10A, which allows the sealingstrength between the cover 20 and the first layer 10A to be increased,so that the easy-open packaging body 1 can be opened easily withoutaffecting the sealing performance.(6) By performing the second heat-sealing step under the conditionhaving temperature and pressure higher than those of the firstheat-sealing step, the dent generated on a position other than thespecific position is not formed in heat-sealing, and thus the peelingdoes not start from the outer circumferential end of the heat-seal part16, so that the packaging body with high reliability can be provided.

The scope of the present invention is not restricted to the embodimentdescribed above, but includes modifications and improvements as long asan object of the present invention can be achieved.

For instance, although the shape of the projected seal part 17 istriangular in the above embodiment, it may be trapezoidal, quadrangular,semicircular and the like.

The shape and size of the tip end and the base end of the projected sealpart 17 are not limited specifically either, but the base end ispreferably rounded in the outer circumferential direction.

Although one projected seal part 17 is formed in the above embodiment,the number is not limited as long as there is one or more projected sealpart 17. When there are a plurality of projected seal parts, theprojected seal parts are preferably arranged at even intervals forapplying balanced stress in peeling.

Although the bent part 14A is a so-called skirt type with the outercircumferential end of the flange merely being bent in the aboveembodiment, a so-called curl type with the outer circumferential endbeing extended vertically downward and bent to have substantiallyC-shaped cross section and the like may also be employed.

When the first layer 10A as the innermost layer of the container body 10is peeled off with the cover 20 in opening, although the layer peelingis generated between the first layer 10A and the second layer 10B as theadjacent layer adjacent to the first layer 10A in the above embodiment,the cohesive peeling may be generated within the second layer 10B.

Although the container body 10 is formed by molding the multilayer sheethaving seven layers, the multilayer sheet may have three to six layersor eight or more layers as long as there are two or more layers.

Although the cover 20 is formed by three layers in the above embodiment,the cover 20 may be formed by a single layer, two layers or four or morelayers.

Although the cover 20 is flat shaped in the above embodiment, the cover20 may be stepped.

Specific structure and shape of the components in the present inventionmay be designed in any manner as long as an object of the presentinvention can be achieved.

The present invention will further be described below with reference toexamples and comparative examples.

Example 1 Multilayer Sheet

Multilayer sheet having seven layers was molded by coextrusion moldingusing resins described below as raw resins of the multilayer sheet usedfor molding the container body 10.

[1] First Layer 10A (Innermost Layer)

[1-1] Raw resin: polypropylene (F734 manufactured by IdemitsuPetrochemical Co., Ltd.)

[1-2] Layer thickness: 70 μm

[2] Second Layer 10B (Adjacent Layer)

[2-1] Raw resin: 60 wt % of polypropylene (E-105GM manufactured byIdemitsu Petrochemical Co., Ltd.) and 40 wt % of low densitypolyethylene (LDPE-fz-038 manufactured by Mitsubishi Corporation.)

[2-2] Layer thickness: 200 μm

[3] Third Layer 10C (Base Material Layer)

[3-1] Raw resin: polypropylene (E-170GM manufactured by IdemitsuPetrochemical Co., Ltd.)

[3-2] Layer thickness: 300 μm

[4] Fourth Layer 10D

[4-1] Raw resin: modified polyolefin adhesive resin (ADMER QB-550manufactured by Mitsui Chemicals, Inc.)

[4-2] Layer thickness: 10 μm

[5] Fifth Layer 10E (Barrier Layer)

[5-1] ethylene vinyl alcohol resin (EVAL manufactured by KURARAY CO.,LTD.)

[5-2] Layer thickness: 40 μm

[6] Sixth Layer 10F

[6-1] Raw resin: modified polyolefin adhesive resin (ADMER QB-550manufactured by Mitsui Chemicals, Inc.)

[6-2] Layer thickness: 10 μm

[7] Seventh Layer 10G (Container Outer Layer)

[7-1] Raw resin: polypropylene (E-170 GM manufactured by IdemitsuPetrochemical Co., Ltd.)

[7-2] Layer thickness: 300 μm

(Container Body)

The above-described multilayer sheet having seven layers was molded intothe container body having the size as shown below by plug assistair-pressure molding.

Inner diameter of opening: 140 mm

Diameter of bottom side: 80 mm

Height: 40 mm

Width of flange: 9 mm

Length of bent part: 3 mm

(Flange)

The inner and outer notches were formed on the flange using ringedheated blades with the distance between the inner and outer notchesbeing 5 mm. The depths of the inner and outer notches were set to besubstantially equal to the thickness of the first layer.

The cover was formed by laminating three layers of cast polypropylene,ethylene vinyl alcohol resin and nylon, in order starting from the sideof the container body. The thickness of the cover was 90 μm.

(First Seal Part)

The first seal part was formed by a seal ring of 2.5 mm, the first sealpart being spaced apart from the inner notch by 1.75 mm. The sealingcondition was as follows; temperature 180° C., pressure 15MPa/container, and time 1.2 seconds.

(Second Seal Part and Projected Seal Part)

The second seal part was provided on the central part of the first sealpart in the width direction with the sealing width of 1.5 mm. When thesecond seal part was formed, the projected seal part was integrallyformed. Two projected seal parts were formed on the two positions of thesecond seal part. The projected seal parts were formed in substantiallytriangular with bottom portion of 6 mm and height of 1 mm, the bottomportion being rounded.

That is, the sealing was integrally provided using a seal ringcorresponding to the second seal part and the projected seal part. Thesealing condition was as follows; temperature 190° C., pressure 15MPa/container, and time 1.2 seconds.

Example 2

Example 2 differed from Example 1 in that the thickness of the firstlayer 10A (innermost layer) was 100 μm instead of 70 μm.

Example 3

Example 3 differed from Example 1 in that the thickness of the firstlayer 10A (innermost layer) was 40 μm instead of 70 μm.

Comparative Example 1

Comparative example 1 differed from Example 1 in that the container washeat-sealed only by the first seal part without forming the second sealpart and the projected seal part. That is, the thickness of the firstlayer 10A (innermost layer) is 70 μm.

Comparative Example 2

Comparative example 2 differed from Example 2 in that the container washeat-sealed only by the first seal part without forming the second sealpart and the projected seal part. That is, the thickness of the firstlayer 10A (innermost layer) is 100 μm.

Comparative Example 3

Comparative example 3 differed from Example 3 in that the container washeat-sealed only by the first seal part without forming the second sealpart and the projected seal part. That is, the thickness of the firstlayer 10A (innermost layer) is 40 μm.

Comparative Example 4

Comparative example 4 differed from Example 1 in that the container washeat-sealed only by the first seal part and a triangular projected partprojected toward the outer circumferential side from the first seal partwithout forming the second seal part. That is, the thickness of thefirst layer 10A (innermost layer) is 70 μm.

Comparative Example 5

Comparative example 5 differed from Example 2 in that the container washeat-sealed only by the first seal part and a triangular projected parttoward the outer circumferential side from the first seal part withoutforming the second seal part. That is, the thickness of the first layer10A (innermost layer) is 100 μm.

Comparative Example 6

Comparative example 6 differed from Example 3 in that the container washeat-sealed only by the first seal part and a triangular projected partprojected toward the outer circumferential side from the first seal partwithout forming the second seal part. That is, the thickness of thefirst layer 10A (innermost layer) is 40 μm.

[Evaluation Method and Evaluation Result]

(Observation of Opening Condition and Result)

After opening the cover of the packaging body obtained by Examples 1 to3 and Comparative examples 1 to 6, the opening conditions were observed.

In Example 1, 100% of the heat-seal part on the cover and the flange wasable to be opened easily.

In Example 2, 70% of the heat-seal part on the cover and the flange wasable to be opened easily.

In Example 3, 100% of the heat-seal part on the cover and the flange wasable to be opened easily. When the cover of Example 3 was peeled off, apart of the first layer (innermost layer) was broken.

In Comparative examples 1 to 3, when the first seal part was displacedtoward either of the inner or outer notch even by 0.1 mm, the cover wasnot able to be opened.

In Comparative example 4 to 6, only 50% of the heat-seal part on thecover and the flange was able to be opened stably.

(Quantitative Evaluation of Sealing Performance and Evaluation Result)

A proximate part of the projected seal part of the packaging body ofExample 1 was cut into a piece of 15 mm width to obtain a sample.Tensile strength of the sample (15 mm width) was measured when thesample was peeled at peeling speed of 50 mm/min and at peeling angle of180° using a tension tester. The tensile strength was 8 N/15 mm width.

When the peeling of the cover and a portion corresponding to the innerside of the container body was measured in the same manner, the tensilestrength was 30 N/15 mm width.

Further, the pressurized air was introduced into the packaging body ofExample 1 to measure the pressure at the time the packaging body wasblown out. The pressure was 0.05 MPa.

INDUSTRIAL APPLICABILITY

The present invention is applicable to an easy-open packaging body thatcan be easily opened by peeling off a cover, especially to a containeror a packaging body filled with contents such as food.

1. A sealed container, comprising: a container body molded from a multilayer sheet; and a cover heat sealed to the container body; wherein: the container body comprises a receptacle for holding contents having an opening, and a flange provided at a circumference of the opening and extending radially outward from the opening; the cover comprises a tab extending radially outward from a remainder of the cover; an innermost layer of the multilayer sheet forming the container body forms an interior surface of the receptacle and an upper surface of the flange; the flange comprises an inner notch and an outer notch; the inner notch extends around the circumference of the opening and protrudes at least partially through the innermost layer of the container body; the outer notch extends around the circumference of the opening and protrudes at least partially through the innermost layer of the container body; the inner notch is closer to the opening of the container body than the outer notch; a section of the innermost layer of the container body provided on the flange between the inner notch and the outer notch is adhered to the cover; the section of the innermost layer is adhered to the cover by: placing the cover in contact with the upper surface of the flange; pressing a first heat seal ring onto the flange via the cover in the section between the inner notch and the outer notch and removing the first heat seal ring; and pressing a second heat seal ring onto the flange via the cover in the section between the inner notch and the outer notch and removing the second heat seal ring; wherein: the second heat seal ring has a narrower profile than the first heat seal ring; the second heat seal ring comprises a projected part extending radially outwardly from a remainder of the second heat seal ring; the second heat seal ring is pressed onto a portion of the flange wholly within a portion of the flange onto which the first heat seal ring was previously pressed; and the projected part of the second heat seal is located in a vicinity of the tab of the cover when the second heat seal ring is pressed onto the flange; and when the cover is removed from the container body by pulling the tab, at least a portion of the section of the innermost layer of the container body provided on the flange between the inner notch and the outer notch is removed from the container body with the cover.
 2. The sealed container of claim 1, wherein the innermost layer of the multilayer sheet comprises polypropylene.
 3. The sealed container of claim 1, wherein the flange comprises a bent part formed by bending an outer circumferential end of the flange.
 4. The sealed container of claim 1, wherein the second heat seal ring is pressed onto the flange at a temperature and a pressure that exceed a temperature and a pressure at which the first heat seal ring is pressed onto the flange.
 5. The sealed container of claim 1, wherein the second heat seal ring is pressed onto the flange at a temperature that exceeds a temperature at which the first heat seal ring is pressed onto the flange by 5° C. or more.
 6. A method for preparing a sealed container, comprising: filling a container body molded from a multilayer sheet with contents; placing a cover on the container body; performing a first heat sealing step to adhere the cover to the container body; and performing a second heat sealing step to adhere the cover to the container body after the first heat sealing step is complete; wherein: the container body comprises a receptacle for holding the contents having an opening, and a flange provided at a circumference of the opening and extending radially outward from the opening; the cover comprises a tab extending radially outward from a remainder of the cover; an innermost layer of the multilayer sheet forming the container body forms an interior surface of the receptacle and an upper surface of the flange; the flange comprises an inner notch and an outer notch; the inner notch extends around the circumference of the opening and protrudes at least partially through the innermost layer of the container body; the outer notch extends around the circumference of the opening and protrudes at least partially through the innermost layer of the container body; the inner notch is closer to the opening of the container body than the outer notch; performing the first heat sealing step comprises pressing a first heat seal ring onto the flange via the cover in a section of the innermost layer of the container body provided on the flange between the inner notch and the outer notch and removing the first heat seal ring; performing the second heat sealing step comprises pressing a second heat seal ring onto the flange via the cover in the area between the inner notch and the outer notch and removing the second heat seal ring; the second heat seal ring has a narrower profile than the first heat seal ring; the second heat seal ring comprises a projected part extending radially outwardly from a remainder of the second heat seal ring; the second heat seal ring is pressed onto a portion of the flange wholly within a portion of the flange onto which the first heat seal ring was previously pressed; and the projected part of the second heat seal is located in a vicinity of the tab of the cover when the second heat seal ring is pressed onto the flange.
 7. The method of claim 6, wherein the innermost layer of the multilayer sheet comprises polypropylene.
 8. The method of claim 6, wherein the flange comprises a bent part formed by bending an outer circumferential end of the flange.
 9. The method of claim 6, wherein the second heat seal ring is pressed onto the flange at a temperature and a pressure that exceed a temperature and a pressure at which the first heat seal ring is pressed onto the flange.
 10. The method of claim 6, wherein the second heat seal ring is pressed onto the flange at a temperature that exceeds a temperature at which the first heat seal ring is pressed onto the flange by 5° C. or more.
 11. A sealed container, comprising: a container body molded from a multilayer sheet; and a cover heat sealed to the container body; wherein: the container body comprises a receptacle for holding contents having an opening, and a flange provided at a circumference of the opening and extending radially outward from the opening; the cover comprises a tab extending radially outward from a remainder of the cover; an innermost layer of the multilayer sheet forming the container body forms an interior surface of the receptacle and an upper surface of the flange; the flange comprises an inner notch and an outer notch; the inner notch extends around the circumference of the opening and protrudes at least partially through the innermost layer of the container body; the outer notch extends around the circumference of the opening and protrudes at least partially through the innermost layer of the container body; the inner notch is closer to the opening of the container body than the outer notch; a section of the innermost layer of the container body provided on the flange between the inner notch and the outer notch is adhered to the cover; the section of the innermost layer includes a first portion having a first thickness and an a second portion having a second thickness; the second thickness is smaller than the first thickness; the second portion has a narrower profile than the first portion; the second portion includes a projected part extending radially outwardly from a remainder of the second portion; the second portion is wholly within the first portion; the projected part of the second portion is located in a vicinity of the tab of the cover; and when the cover is removed from the container body by pulling the tab, at least a portion of the section of the innermost layer of the container body provided on the flange between the inner notch and the outer notch is removed from the container body with the cover.
 12. The sealed container of claim 11, wherein the innermost layer of the multilayer sheet comprises polypropylene.
 13. The sealed container of claim 11, wherein the flange comprises a bent part formed by bending an outer circumferential end of the flange. 